To estimate the proportions of US infants who were breastfed exclusively for 6 months, according to characteristics of the mother, child, and household environment, and to compare associations between those characteristics and exclusive breastfeeding with associations between those characteristics and breastfeeding initiation. Data were obtained from the 2007 National Survey of Children's Health, a nationally representative, cross-sectional survey. Multivariate logistic regression was used to calculate the adjusted odds ratios for breastfeeding among all infants and for breastfeeding exclusively for 6 months among infants who had initiated breastfeeding. All analyses were limited to children aged 6 months through 5 years for whom breastfeeding data were available (N = 25 197). Of the nearly 75% of children in the study who had ever been breastfed, 16.8% had been breastfed exclusively for 6 months. Non-Hispanic black children were significantly less likely to have ever been breastfed compared with their non-Hispanic white counterparts (adjusted odds ratio: 0.54 [95% confidence interval: 0.44-0.66]). However, no significant differences in the odds of exclusive breastfeeding according to race were observed. Children with birth weights of <1500 g were most likely to have ever been breastfed and least likely to have been breastfed exclusively. Maternal age was significantly associated with exclusive breastfeeding; however, maternal age was not associated with breastfeeding initiation. In the United States, the prevalence of exclusive breastfeeding for 6 months remains low among those who initiate breastfeeding. Factors associated with breastfeeding exclusively for 6 months differ from those associated with breastfeeding initiation.
